Electromagnetic radiation, such as microwave radiation, is a known mechanism for delivering energy to an object. The ability of electromagnetic radiation to penetrate and heat an object both rapidly and effectively has proven advantageous in many chemical and industrial processes. Further, because the use of microwave energy as a heat source is generally non-invasive, microwave heating is particularly useful in processing ‘sensitive’ dielectric materials, such as food and pharmaceuticals, and can even be useful for heating materials having a relatively poor thermal conductivity, such as wood. However, the complexities and nuances of safely and effectively applying microwave energy, especially on a commercial scale, have severely limited its application in several types of industrial processes.
Because of its wide suitability for a variety of applications, its renewable nature, and its relatively low cost, wood is one of the most widely used building materials in existence. However, because wood is a natural product, its physical and structural properties can vary substantially, not only amongst different species, but also amongst different trees, or even different locations within the same piece of wood. Further, wood is generally hygroscopic, which affects its dimensional stability, and its biochemical composition makes it susceptible to attack by insects and fungi. As a result, several types of wood treatment processes have been developed to increase the stability of wood through modification of its chemical, physical, and/or structural properties. Examples of treatment processes include impregnation treatments, coating treatments, thermal modification, and chemical modification. The latter two treatment processes generally alter the properties of wood to a more drastic degree than the others and, consequently, these types of processes typically involve more complex schemes and systems. For example, many chemical and thermal treatment processes can be carried out under vacuum and/or in the presence of one or more treatment chemicals. As a result, commercialization of these types of technologies has been limited, and multiple challenges remain to be overcome in order for these processes to be industrialized on a wide scale.
Thus, a need exists for a more efficient and cost effective commercial-scale system suitable for chemically or thermally treating wood. A need also exists for an efficient and cost effective industrial-scale microwave heating system suitable for use in a wide variety of processes and applications, including the treatment of wood.